Let \(\mathfrak {M}\)  stand for the linear space of all real-valued (signed) Radon measures \(\xi \)  on \(\mathbb {R}^n\)  such that (REF ) is fulfilled with \(\mu \)  replaced by \(|\xi |:=\xi ^++\xi ^-\) , where \(\xi ^+\)  and \(\xi ^-\)  denote the positive and negative parts of \(\xi \)  in the Hahn–Jordan decomposition. Then the potential \(\kappa _\alpha \xi \)  of any \(\xi \in \mathfrak {M}\)  is well defined and finite n.e. on \(\mathbb {R}^n\)  (actually, even everywhere on \(\mathbb {R}^n\)  except for a polar set, see [1]}).
